QoS

QoS Models

best effort

Integrated Services (IntServ)

Differentiated Services (DiffServ)

Mechanisms

classification

marking

policing

shaping

Why?

Lack of bandwidth

Latency and jitter

Packet loss

Increase the link bandwidth capacity

policing and queueing to prioritize traffic according to level of importance

the time it takes for packets from a source to a destination

400 ms should not be exceeded

real-time traffic should be less than 150 ms

Increase link speed

Implement QoS

traffic policing to drop low-priority

traffic shaping to delay packets instead of dropping

not recommended for real-time traffic

can cause jitter

used for traffic that does not require any special treatment.

make a bandwidth reservation and to indicate that they require special QoS treatment

network identifies classes that require special QoS treatment.

for real-time applications such as voice and video

Resource Reservation Protocol (RSVP):

Used to reserve resources throughout a network

Provides call admission control (CAC)

no other IP traffic can use

Any bandwidth reserved and not used is wasted

requires all nodes, including the endpoints support, build, and maintain RSVP path state for every single flow.

does not scale well on large networks

have thousands or millions of flows due to the large number of RSVP to be maintained

start by RSVP PATH messages

receiver source address

destination address

bandwidth to reserve

stored in the RSVP path state of each node

no need signaling protocol

highly scalable since no RSVP flow state to maintain

as bandwidth and delay are managed on a hop-by-hop

divides IP traffic into classes and marks it
Each of the classes can be assigned a different level of service

Layer 7 Classification
Next Generation Network-Based Application Recognition (NBAR2)

Protocol Discovery enables discover and get real-time statistics on applications currently running

Modular QoS CLI (MQC) traffic matching a specific network protocol be placed into one traffic class

different QoS policies can be applied to the different classes of traffic.

QoS mechanism that colors a packet by changing a field within a packet or a frame header with a traffic descriptor